In an upcoming study in the Columbia Law Review, researchers examined approximately 2,000 interventions by activist hedge funds from 1994 to 2007.

"We find no evidence that interventions are followed by declines in operating performance in the long term; to the contrary, activist interventions are followed by improved operating performance during the five-year period following these interventions, the researchers write.

"We also find no evidence that the initial positive stock price spike accompanying activist interventions fails to appreciate their long-term costs and therefore tends to be followed by negative abnormal returns in the long term; the data is consistent with the initial spike reflecting correctly the intervention’s long-term consequences."